Measurement of polymerization reractions



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Us. 2 BYHMQWMVM A T TORNEVS @March 7, 1961 l.. w. MORGAN MEASUREMENT oF PoLYMERIzATIoN REACTIONS 9 Sheets-Sheet 3 Filed NOV. 21, 1957 INVENTOR. L..W. MORGAN A 7'7'0RNEYS LII March 7, 1961 Filed Nov. 21. 1957 L. W. MORGAN MEASUREMENT OF POLYMERIZATION REACTIONS 9 Sheets-Sheet 4 March 7, 1961 L. W. MORGAN MEASUREIIIIENT OF POLYMERIZATION REACTIONS Filed NOV. 21, 1957 9 Sheets-Sheet 5 I I I I I I I I 201C 2mb zolc 2I2cxJ AMPLIFIER AMPLIFIER AMPLIFIER 209 I I (21o I I fm1 INVENTOR. Lw. MORGAN F/G. Z BY March 7, 1961 w. MORGAN MEASUREMENT 0F POLYMERIZATION REACTIONS 9 Sheets-Sheet 6 Filed NOV. 21, 1957 .N R .S mm n M WM /MO m w L N Awww 1% H v.. B Av ON March 7, 1961 L. w. MORGAN 2,974,017

MEASUREMENT 0F' POLYMERIZATION REACTIONS Filed NOV. 21, 1957 9 Sheets-Sheet '7 w. www? INVENTOR. L.W. MORGAN A TTORNEVS 'AAAAAAg W v W om- March 7, 1961 L. w. MoRGAN MEASUREMENT oF POLYMERIZATION REACTIONS 9 Sheets-Sheet 8 Filed NOV. 21, 1957 mmm INVENTOR L W MO RGAN March 7, 1961l w. MORGAN MEASUREMENT oF PoLYMERIzATIoN REACTIONS 9 Sheets-Sheet 9 Filed Nov. 21, 1957 INVENTOR. L.W. MORGANV -f l A 7' TORNE V5 MEASUREMENT OF POLYMERIZATION REACTIONS Lyman W. Morgan, Bartlesville, Okla., assignor to Phil- This invention relates to apparatus for measuring the concentration of polymer in polymerization reactors.

Various methods are known for producing normally solid and semisolid polymers. For example, hydrocarbons, such ethylene, propylene, isobutene, butadiene and styrene can be polymerized, either independently or in various admixtures with one another, to produce solid or semisolid polymers. Recently, considerable attention has been directed toward the production of solid olefin polymers such as polymers of ethylene and/or propylene. The polymerizations are frequently carried out in the presence of a solid catalyst, utilizing a liquid solvent as the reaction medium. The polymerization reactions are exothermic so that it becomes necessary to provide for the removal of heat liberated by the reaction. The removal of the heat of reaction is often accomplished by employing a reactor provided with an indirect heat exchange means through which a suitable coolant is circulated. One of the problems which occurs when using such a system involves controlling the polymerization reaction rate so that a uniform product having desired properties is obtained.

In accordance with the present invention, apparatus is provided for measuring the concentration of polymer in the reactor. The measurement is based on the rate of polymer production. This, in turn, can be measured by the heat liberated by the polymerization reaction, which measurement can be made by subtracting the heat supplied to the reactor from the heat removed from the reactor. Measurements are made of the flow rates and temperatures of all the principal streams entering and leaving the reactor. Other sources of heat addition and heat losses are also measured to provide an indication of the total amount of heat entering and leaving the reactor. Computing apparatus is provided for solving sequentially the several heat balance equations which represent the amounts of heat entering or leaving the reactor from the several process streams. 'Ihis requires the solution of a plurality of multiplications in sequence. An adding, multiplying and integrating circuit utilizes this information and a measurement of product ilow to compute the polymer concentration in the reactor.

Accordingly, it is an object of this invention to provide apparatus for use in measuring the polymer concentration in polymerization reactors.

Another object is provide novel integrating apparatus.

Other objects, advantages and features of the invention should become apparent from the following detailed description whch is taken in conjunction with the accompanying drawing in which:

Figure 1 is a schematic circuit drawing of a polymerization reactor having apparatus of this invention associated therewith.

Figure 2 is a schematic circuit drawing showing the detecting elements of Figure 1.

Figure 3 is a schematic circuit drawing of a portion Patent() `ice of the computer which establishes signals representative of heats supplied to the reactor by the inlet streams.

Figure 4 is a schematic circuit drawing of the input terminals of the computer and a portion of the automatic balancing mechanism.

Figure 5 is a schematic circuit drawing showing a second portion of the automatic balancing mechanism.

Figure 6 is a schematic circuit drawing of a portion of the computer timing mechanism. y

Figure 7 is a schematic circuit drawing of one of the addition channels of the computer.

Figure 8 is a schematic circuit drawing of the summing and calibration network employed in the computer.

Figure 9 is a schematic circuit drawing of a second portion of the timing mechanism.

Figure 10 is a schematic circuit drawing of the polymer concentration computing network.

The present invention is broadly applicable to polymerization processes in general, and more particularly to processes in which an olefin is contacted with a catalyst in suspension in a solvent. The invention is especially applicable for use in controlling the production of polymers as described in the copending application of Hogan and Banks, Serial No. 476,306, tiled December 20, 1954, now abandoned. As set forth in this copending application in greater detail, unique polymers and copolymers can be produced by contacting one or more olefins with a catalyst comprising, as an essential ingredient, chromium oxide, preferably including a substantial amount of hexavalent chromium. The chromium oxide is ordinarily associated with at least one other oxide, particularly at least one oxide selected from the group consisting of silica, alumina, zirconia and thoria. The amount of chromium, as chromium oxide, in the catalyst can range from 0.1 to 10 or more weight perv cent. Although chromium contents as high as 50 weight 1 several hours at a temperature of from about 450 to 1500a F., preferably from about 900 to 1000 F.,' forV percent are operative, amounts above l0 weight percent appear to have little added advantage for the polymerization of ethylene. However, for the polymerization of propylene and higher boiling olens, chromium contents as high as 25 or 30 percent are often advantageous. One satisfactory method for producing the catalyst involves the use of a steam-aged commercial cracking catalyst comprising a coprecipitated gel containing approximately weight percent silica and 10 weight -percent alumina.A

Such a gel is impregnated with an aqueous solution of a chromium compound ignitable to chromium oxide. Examples of such compounds are chromium trioxide,

chromium nitrate, chromium acetate and ammoniumchromate. The composite resulting from the impregnation step is dried and then contacted for a period of example, with a stream of a substantially anhydrous oxygen-containing gas, such as air.

The 'olcn feed for the polymerization 'comprises at least one olen selected from the class of l-oletlns having a maximum of 8 Carbon atoms per molecule and no branching nearer the double bond than the 4-position. Examples of such olens include ethylene, propylene, .lbutene, 1-pentene and 1,3-butadiene. Copolymers, such as ethylene-propylene copolymers and ethylene-butadiene .Copolymers, can be prepared by the described method. The polymerization can be effected at a temperature in the range to 450 F. The pressure can range fromy approximately atmospheric to as high as 1000 p.s.i.

A satisfactory method of conducting the polymerization as disclosed in the above mentioned patent application comprises contacting an olefin with a slurry of catalyst in a hydrocarbon solvent which can exist as a liquid at the temperature of polymerization. In such a procedure, `the reaction pressure need only be suiicient ,Patented Mar. 7 `1 961 I to maintain the solvent substantially in the liquid phase, and ordinarily ranges from about 100 to 700 p.s.i. The control system of the present invention is particularly applicable to this type of operation, i.e., one in which an olefin is contacted with -a catalyst slurry. When utilizing the present control method with this type of process, it has been found to be desirable [to operate at a temperature such that the polymer is substantially all in solution in the hydrocarbon solvent. This temperature will vary according to the particular solvent which is utilized, eg., with parafns between about 250 and 450 F., and with naphthenes between about 230 and 450 F. However, it is to be understood that the method can be used with processes carried out at temperatures such that the polymer produced is in undissolved solid form.

Suitable solvents for use in the above described process are hydrocarbons which are liquid and chemically inert under the reaction conditions. Solvents which can be employed advantageously include paratiins, such as those having from 3 to 12, preferably from 6 to 9, carbon atoms per molecule, for example, 2,2,4-trimethylpentane (isooctane), normal hexane, normal decane, isopentane, and the like. Another class of solvents which can be employed are naphthenic hydrocarbons having from 5 to 6 carbon atoms in a naphthenic ring and which can be maintained in the liquid phase under the polymerization conditions. Examples of such naphthenic hydrocarbons include cyclohexane, cyclopentane, methylcyclopentane, methylcyclohexane, ethylcyclohexane, the methyl ethyl cyclopentanes, the methyl propyl cyclohexanes, and the ethyl propyl cyclohexanes. The described class of naphthenic hydrocarbons includes condensed ring compounds such as decalin and the alkyl derivatives thereof. A preferred subclass of naphthenic hydrocarbons within the above defined general class comprises those naphthenic hydrocarbons having from 5 to 6 carbon atoms in a single ring and from 0 to 2 methyl groups as the only substituents on the ring. Thus, the preferred naphthenic hydrocarbon solvents are cyclopentane, cyclohexane, methylcyclopentane.

Referring now to Figure l of the drawing, there is shown a ow diagram which illustrates diagrammatically a preferred embodiment of a portion of the computer of the present invention. While the invention is described in conjunction with a particular polymerization process, it is to be understood that it is not intended to so limit the invention. The invention is applicable to any polymerization process in which the material to be polymerized and catalyst are continuously supplied to a polymerization reaction zone.

`As shown in Figure l, a suitable solvent, such as cyclohexane, enters a polymerization reactor through an inlet conduit 31 at a temperature of 234 F. This solvent enters the system at a rate of 237,000 pounds per day and has a composition in weight percent as follows:

Methane Trace Ethylene 0.86 Ethane 0.07 Cyclohexane 99.07

Methane 0.3 8 Ethane 2.80 Ethylene 95.32 Cyclohexane 1.50

A catalyst enters reactor 30 through an inlet conduit 33, In the particular reaction referred to by way of example, the catalyst is added to the system in the form of a slurry in the solvent, 96% cyclohexane and 4% catalyst. This catalyst is a chromium oxide-silica-alumina catalyst prepared by impregnating a Weight percent silica and l0 weight percent aluminum gel composite with chromium trioxide which is dried and heated in air to form a composition containing approximately 2.5 weight percent chromium in the form of chromium oxide, of which approximately one-half is in the form of hexavalent chromium. The catalyst is added at the rate of 2,725 pounds of slurry per day.

Reactor 30 is surrounded by a jacket 34 through which a coolant is circulated. A coil of heat exchange tubes 35 is disposed within the interior of reactor 30. Cooling coil ,35 and jacket 34 thus provide a means for removing heat from reactor 30 during the polymerization. Reactor 30 is provided with a stirrer 36 which is driven by a motor 37. Motor 37 is energized from a source of electrical energy, not shown, which is connected to the motor by means of a cable 38. The reactor effluent is withdrawn through a product conduit 40. This efliuent, comprising a mixture of polymer, solvent, spent catalyst and unreacted ethylene, is subsequently passed to suitable separation meansto recover the desired polymer.

The reaction mixture in reactor 30 is maintained at a desired temperature by circulating a coolant through jacket 34 and coils 35. It is desirable to employ the same material, cyclohexane, for the coolant as is employed for the solvent. This eliminates any additional separating problems if leakage should occur between the coolant conduits and the interior of the reactor. The coolant is introduced into the system through an inlet conduit 41 which communicates with jacket 34 and coils 35. The coolant is subsequently removed from the system through a conduit 42 which communicates with a ash tank 43. Vapor is removed from flash tank 43 through a conduit 44 which communicates with the inlet of a condenser 45. The condensed vapors are returned to tank 43 through a conduit 46. The liquid in tank 43 is returned to reactor 30 through conduit 41. In order to simplify the drawing, the various pumps and valves and other controllers necessary to establish and control the ows of materials have been deleted.

From an inspection of Figure 1, it should be evident that heat is added to and removed from reactor 30 in several ways. In order to determine the production rate, the total heat liberated by the polymerization reaction is computed. This computation is made by subtracting the heat which enters the reactor from the heat which is withdrawn from the reactor. The amounts of these heats are obtained by summing a series of equations which represent the heat transferred into and out of reactor 30.

The rst source of heat removal from reactor 30 results from the solvent supplied by conduit 31. This heat Q1 can be calculated from the following equation:

K1=an orifice constant pTo=density at To a1=density temperature coefficient To=a reference temperature Ts=temperature of the solvent APV- pressure dilerential across an orifice in conduit 31 C1=specif`1c heat of the solvent at T1 1=specific heat temperature coefficient TAve.=average temperature, defined hereinafter T0=a reference temperature ATS=temperature difference, defined hereinafter, see

Figure 2 The heat Q2 removed from the reactor by the coolant is represented as follows:

The sensible heat Q3 removed vby cooling of thecondensed vapors from ash tank 43 is represented as follows:

K3==an oriiice constant Y TM=temperature of coolant in conduit 46 a2=density temperature coefiicient AP3=pressure differential across an orifice in conduit 46 ATM=temperature difference, defined hereinafter, see

Figure Z.

Heat is also removed from reactor 30 due to conduction through the insulated walls of the reactor. This heat loss Q4 can be represented as follows:

where K4=a constant V=temperature difference across reactor walls.

The major amount of heat removal results from the heat of vaporization of the coolant. This is represented as follows:

Q8: (KWLoad""KWNo Load) X3-413 (7) where:

KWLoadv=energy supplied to motor 37 without a load on the stirrer KWNo Lod=energy supplied to motor 37 with a load on Ithe stirrer 3.413=Bt.u. per kw. hour.

The heat Q7 removed by the catalyst slurry is assumed to be constant. Heat is also supplied to reactor 30 due to the heat of solution of the olefin in the solvent. This is represented yas follows:

Q9=Flow Ks (8) Where:

K6=constant relating Ito heat of solution.

The various quantities indicated in the foregoing equations are measured by the apparatus illustrated schematically in Figure 1. The temperatures of the materials flowing through conduits 31, 32, 41 and 46 are measured by temperature sensing elements TS, TE, TC and TM, respec tively. The temperature within reactor 30 is measured by a temperature sensing element TR. The temperatures of the liquid and vapor in tank 43 are measured Aby respec- ,i

tive temperature sensing elements TF and Tv. Theheat loss through the reactor walls is measured by a sensing element L. The heat generated by stirrer 36 is measured in terms of the power supplied to motor 37. This power is measured by a wattmeter KW which can be a thermal converter of the type described in Bulletin 77-39-0-2 of Leeds & Northrup Company, Philadelphia, Pa., for .ex--

ample. The flow rates through conduits 31, 41 and 46 are measured in terms of pressure differences across orifices in the respective conduits. These pressure measurements are made by respective detecting elements AP1, AP2, and AP3. The outputs of the several detecting elements of Figure 1 are applied to a computer 48 which provides a measurement of the polymer concentration.

The various temperatures which are measured by the apparatus of Figure 1 can be conveniently obtained by means of thermocouples. These various thermocouples are illustrated schematically in Figure Z. Certain of these thermocouples are provided with cold junctions which are indicated by primed reference characters. Two separate thermocouples are employed to measure the temperature within reactor 30. These thermocouples are designated as TR and TR1. The terminals of these various thermocouples are connected in the manner illustrated in Figure 2 to provide the various quantities indicated adjacent the respective terminals which `are designated 5a and 5b, 2a and 2b, 3a and 3b, 13a and 13b, 12a and 12b, 9a and 9b, 8a and 8b, and 6a and 6b. The three differential pressure measurements are `applied in sequence to a fiow transducer 55. The output of transducer 55 is connected between terminals 4a and 4b, 7a and 7b, and 10a and 10b.

The heat loss through the reactor walls is measured by a series of spaced thermocouples L having first junctions near the inner walls and second junctions near the outer walls. The outputs of these thermocouples thus provide signals which are representative of the heat transferred through the reactor walls. This signal is applied between terminals 11a and 11b. The output signal of wattmeter KW is applied between terminals 14a `and 14b. The output signal of fiowmeter 47, which provides a signal directly related to ethylene flow, is applied rthrough a transducer 56 to terminals 15a and 15b. As will become apparent from the detailed `description which follows, the several output signals from the apparatus of Figure 2 are al1 direct current voltages. These voltages constitute `the inputs to the computer.

In the described example, TE, TS, TV, TF, TM, TR and TC are approximately 260 F., 234 F., 230 F., 228 F., F., 280 F. and 229 F., respectively. KWLoad is 35 kw. and KWNo Load is 5 kw. Reactor 30 has a volume of 3300 gallons. I

The detecting elements API, AP2 and AP3 providefoutput alternating current signals which are representative of the pressure ditferences across the respective orifices.

Suitable elements for this purpose are described in Bulle-1 tin A-707, 'Ihe Swartwout Company, Cleveland, Ohio.

These signals are converted by flow transducer 55 into direct voltages which are proportional to the respective iiows. With reference to Figure 3, the first output terminal of ow detecting element APs is connected to the K first end terminal of potentiometer 61. The second output terminal of detecting element AP3 is connected to the second end terminal of potentiometer 61 and to ground. The contactor of potentiometerl is connected to a terminal 62 which is adapted to be engagedby a switch 63. Switch 63 is actuated by a relay 64. Flow indicating elements AF2 and All are likewise connected across respective potentiometers 65 and 66. The contactor of potentiometer 65 is connected to a terminal 67 which-is engaged by switch 63 when relay 64 is energized. The contactor of potentiometer 66 is connected to a terminal 68 Iwhich is engaged by a switch 69 when relay 64 is not energized. Switch 63 is connected to a terminal 70 which isengaged by a switch 7-1 when a relay 72is 'not enen.

gized. Switch 69 is connected to a'terminal 73 which is engaged by a switch 74 when relay 72 is energized. Switches 71 and 74 are connected to the first input terminal of an alternating current amplifier 75, the second input terminal of which is connected to ground. Potentiometer 65 actually is not required in the specific example described, and can eectively be eliminated by moving its contactor to the uppermost position.

Relays 64 and 72 are energized selectively by a circuit described in detail hereinafter. When both relays 64 and 72 are deenergized, potentiometer 61 is connected to its amplifier 75. When relay 64 alone is energized, potentiorneter 65 is connected to amplifier 75. When relay 72 alone is energized, potentiometer 66 is connected to amplifier 75. A reference voltage is connected to amplifier 75 when 64 and 72 are energized. The potentiometers 61 and 66 are employed to multiply the pressure difference signals by density correction factors.

The first output terminal of amplier 75 is connected through a capacitor 76 to the first end terminal of the primary winding of a transformer 77. The second output terminal of amplifier 75 is connected to ground and to the second end terminal of the primary winding of transformer 77. The end terminals of the secondary windings of transformer 77 are connected to the control grids of triodes 78 and 79, respectively. The centertap of the secondary Winding of transformer 77 is connected to ground. A resistor 81 is connected in parallel with the secondary winding of transformer 77. The anodes of triodes 78 and 79 are connected to a terminal 82 which is maintained at a positive potential. The cathodes of triodes 78 and 79 are connected to ground through respective resistors 83 and 84. A source of alternating current 85 of the same frequency as the output signals from APl, APZ and AP3 is applied across the primary winding of a transformer 86. The first end terminal of the secondary winding of transformer 86 is connected through capacitors 87 and 88 to the cathodes of triodes 78 and 79, respectively. The second end terminal of the secondary winding of transformer 86 is connected to ground. The cathode of triode 79 is connected through series connected resistors 90 and 91 to the first input terminal of a direct current amplifier 92. The cathode of triode 78 is connected through series connected resistors 93 and 94 to the second input terminal of amplifier 92. A capacitor 95 is connected between ground and the junction between resistors 90 and 91 and a capacitor 96 is connected between ground and the junction between resistors 93 and 94.

Triodes 78 and 79 and the circuit elements associated therewith thus form a phase sensitive detector which provides an output direct voltage of magnitude proportional to the alternating input voltage. The output signals from the cathodes of the two tubes are filtered so that a smooth direct voltage is supplied to the input of amplifier 92. The remainder of the circuit illustrated in Figure 3 with the exception of elements 250 to 253 is provided to obtain a signal proportional to the square root of the output signal from amplifier 92.

The first output terminal of amplifier 92 is connected through a resistor 100, a variable resistor 101, a resistor 102 and a capacitor 103 to the control grid of a triode 104. The control grid of triode 104 is connected to a negative potential terminal 108 through a resistor 117. Resistor 101 is shunted by a non-linear resistance element 105. The cathode of triode 104 is connected to the cathode of a triode 106. These two cathodes are connected through a resistor 107 4to a terminal 108 which is maintained at a negative potential. The anode of triode 104 is connected to a Iterminal 109 which is maintained at a positive potential. The anode of triode 106 is connected to terminal 109 through a resistor 110 and to the control grid of a triode 111 through a resistor 112. The control grid of triode 111 is connected to ground through a resistor 113. The cathode of triode 111 is connected to the ground through a resistor 114 which is shunted by a capacitor 115. The anode of triode 111 is connected to terminal 109 through a resistor 116. The cathode of triode 111 is also connected to the cathode of a triode 118 through a resistor 119. The anode of triode 118 is connected to terminal 109, and the cathode of triode 118 is connected through a resistor 120 to terminal 108. The cathode of triode 118 is connected through a resistor 121 to output terminals 4a, 7a, and 10a. The cathode of triode 118 is also connected to the junction between resistor =102 and capacitor 103 through a resistor 122 and a second non-linear resistance element 123.

Triodes 104, 106 and 111 and the circuit elements associated therewith thus provide an operational amplifier wherein the output signal is a function of the square root of the input signal. This is accomplished by means of the non-linear resistance elements in the input circuit and in the feedback circuit. These elements are selected so that the current flows therethrough are an inverse exponential function of the voltages applied across the elements.

A stabilizing amplifier is provided in the circuit of Figure 3 to avoid drift in the direct current operational amplifier. The junction between resistor 102 and capacitor 103 is connected through a resistor 125 to the first contact 126 of a vibrator assembly. The second contact 127 is connected to ground. A switch 128 vibrates between contacts 126 and 127 when a coil 129 is energized by a source of alternating current 130. Contact 126 is connected through a capacitor 131 to the control grid of a triode 132. Switch 128 is connected through a capacitor 133 and a resistor 134 to the anode of a triode 135. The anodes of triodes 132 and 135 are connected through respective resistors 136 and 137 to a terminal 138 which is maintained at a positive potential. The cathodes of triodes 132 and 135 are connected to ground through respective resistors 140 and 141. The control grids of triodes 132 and 135 are connected to ground through respective resistors 142 and 143. The anode of triode 132 is connected through a capacitor 144 to the control grid of triode 135. A capacitor 145 is connected between the anode of triode 132 and ground. Switch 128 is also connected through a resistor 146 to the control grid of triode 106. The control grid of triode 106 is connected to ground through a capacitor 147. The anode of triode 111 is connected to the control grid of triode 118 through a capacitor v150 which is shunted by a resistor 151 and electrical dischargetubes 152 and 153 which are connected in series relationship. The control grid of triode 118 is connected to ground through a resistor '154.

The alternating current amplifier thus formed by triodes 132 and 135 forms a feedback network in the direct current amplifier in order to stabilize the direct current amplifier against drift.

The direct voltages which appear between the several pairs of terminals of Figure 2 are converted into corresponding potentiometer settings in order to perform the multiplications required to solve the heat transfer equations. These voltages are converted into the respective potentiometer settings in sequence and repetitively by means of a stepping switch. The circuit employed to establish the potentiometer settings is illustrated schematically in Figures 4 and 5. The output terminals of Figure 2 are represented in Figure 4 as the a and b terminals of the stepping switch. The a terminals are engaged in sequence by switch arm A and the b terminals are engaged in sequence by switch arm B. The switch arms move between adjacent terminals each time a solenoid 150 is energized. The stepping switch preferably is of the rotary type so that the switch arms move successively to adjacent contacts and then repeat the operation. The stepping switch employed in one particular embodiment of this invention had 25 contacts associated with each switch arm. The computing operation of the described example can be accomplished with less contacts, althoughn some of the additional contacts are employed in the'V calibration steps described hereinafter.

Switch arm A is connected to a terminal 151 which is engaged by a switch 152 when a relay 153 is deenergized. Switch arm A is also connected to a terminal 154 which is engaged by a switch 155 when a relay 156 is deenergized. Switch 155 is connected through a resistor 157 to switch arm D of the stepping switch. Switch arm B is connected to a terminal 158 which is engaged by switch 159 when relay 153 is deenergized. A resistor 404 and a capacitor 405 rareconnected in parallel between switch arm B and ground. Switch arm B is also connected to a terminal 161 which is engaged by a switch 162 when relay 156 is deenergized. Switch 162 is connected to a terminal 164 which is engaged by switch 165 when a relay 166 is deenergized. Switch 165 is connected to the first input terminal of servo amplifier 168. The second input terminal of amplifier 168 is connected to switch arm C of the stepping switch. A capacitor 169 is connected between terminal 164 and switch arm D. The first output terminal of amplifier 168 is connected to a terminal 170 and to a switch 171 which engages a terminal 172 when a relay 173 is energized. VTerminal 172 is connected to the first input terminal of a servo motor 174. The second output terminal of amplifier 168 and the second input terminal of motor 174 are grounded.

Terminals 1c and 2c of the stepping switch are connected to a terminal 176; terminals 1e and 2e are connected to la terminal 177; terminals 1f and 2f are connected to a terminal 178; and terminals 1d and 2d are connected to a terminal 179. A variable resistor 180, a resistor 181, and a battery 182 are connected in series relationship between switch arms E and F. A resistor 183 and a standard cell 184 are connected in series relationship between switch arm E and a terminal 185 which is engaged by switch 165 when relay 166 is energized. Terminals 176, 177, 178 and 179 are connected to the circuit illustrated in Figure 5. Terminal 176 is connected to the junction between resistors 180 and 181. The second terminal of resistor 180 is connected to terminal 178, and the second terminal of resistor 181 is connected to terminal 177. A resistor 183', a potentiometer 184',

land a resistor 185 are connected in series relationship between terminals 178 and 177. Resistors 186 and 187 are connected in parallel with the potentiometer 184. Terminal 179 is connected by means of a conductor 188 which forms a temperature compensating thermocouple cold junction, to the contactor of potentiometer 184.

Terminal 170 of Figure 5 is connected to a switch 190 which engages a terminal 191 when a relay 192 is energized. Terminal 191 is connected through the rst coil 193 of a reversible two-phase induction motor 194 to ground. One terminal of the second coil 195 of motor 194 is connected to terminal 196. The second terminal of coil 195 is connected to a terminal 197 which is engaged by a switch 198 when relay 192 is energized. Switch 198 is connected to a terminal 199. An alternating current source described hereinafter is connected between terminals 196 and 199. The drive shaft of motor 194 is connected to the contactor of potentiometer 184. The drive shaft of motor 194 is also connected to the contactors of potentiometers 201 and 202.

The circuit of Figures `4 and 5 forms a self-balancing potentiometer. The input signal appears between the first input terminal of amplifier 168 and switch arm D. This signal is balanced against a reference voltage in the bridge network so that any potential difference energizes motor 194 through amplifier 168. 'Ihis portion of the circuit of Figures 4 and 5 comprises a conventional balancing circuit of the general type described in Bulletin No. B15-13, Minneapolis-Honeywell Regulator Co., Brown Instrument Division, Philadelphia, Pa. If the input signal differs from the reference voltage, motor 194 is energized to adjust the position of the contactor of potentiometer 184. 'Ihis adjustment continues until the circuit is restoredto a set of balance. The rotation of motor 194 required to establish this balance is, therefore, a function of the magnitude of the input signal. This rotation also establishes the positions of the contactors 4of potentiometers 201 and 202.

The computer is also provided with thirteen additional Y .reset the potentiometers representative of changes in the variables to be measured.

One of the networks employed to perform the multiplication required to solve the heat transfer equations indicated above is illustrated in Figure 7. A source of alternating current 205 is connected across a potentiometer 206. The primary winding of a transformer 207 is connected between the contactor and one end terminal of potentiometer 206. The secondary winding of transformer 207 is connected across a potentiometer 201a. A potentiometer 208, having a grounded center tap, is connected across the secondary winding of transformer 207. The contactor of potentiometer 201a is connected to the first input terminal of an isolation amplifier 209. The first output terminal of amplifier 209 is connected to the first end terminal of a potentiometer 201b. The second end terminal of potentiometer 201b is connected to ground. The contactor of potentiometer 201b is Vconnected to the first input terminal of an isolation amplifier 210. The first output terminal of amplifier 210 is connected to the first end terminal of potentiometer 201e. The second end terminal of potentiometer 201C is connected to ground. The contactor of potentiometer 201e is connected to the first input terminal of an amplifier 211. The first output terminal of amplifier 211 is connected to an output terminal 212a. The second output and input terminals of amplifiers 209, 210 and 211 are connected to ground.

With reference to Equation l, it can be seen that there rare three principal quantities to be multiplied to obtain the product. These three Variables are represented by the three potentiometers 2010, 201b and 201C of Figure 7. The indicated multiplication is provided by these three cascade connected potentiometers. The isolation amplifiers are employed .to prevent current from being drawn from the potentiometers. `Circuits similar to the circuit of Figure 7- are provided for each of the other heat transfer equationsrto be solved. The equations which have fewer than three variables to be multiplied require fewer potentiometers. These circuits are otherwise similar to the circuits of Figure 7.

'I'he output signals of the plurality of multiplying circuits of the form of Figure 7 are applied to terminals 212a, 212b 212i ofFigure 8. These terminals are connected through respective resistors 213a, 213b 213i to the first input terminal of a summing amplifier 480. The first output terminal of amplifier 480 is connected through a capacitor 214 to the first input terminal of a recorder-controller 215. The second input terminal of controller 215 is connected to ground. The signal applied to controller 215 represents the amount of heat liberated by the polymerization reaction. This is obtained from the addition of the heat transfer equations, plus or minus, depending upon whether heat is added or subtracted. This signal is applied through a conventional control medium to regulate either valve 50 or valve 51. If the indicated heat .of reaction should increase, the rate of addition of olefin or catalyst to the reactor is decreased. If the indicated heat of reaction 11 should decrease, the ow of olen'or catalyst is increased; It is thus possible to maintain the reaction at a steady rate which results in the production of polymer of uni-V form quality. This control operation is described in greater detail hereinafter.

Servo amplifier 16S is illustrated in Figure 6. The first input terminal 220 (connected to switch 165 of Figure 4) is connected to a switch 221 which vibrates between contacts 222 and 223 when a coil 224 is energized by a source of alternating current 225. Contacts 222 and 223 are connected to the respective end terminals of the primary winding of a transformer 226. The second input terminal 227 (connected to switch `C of Figure 4) of amplifier 168 is connected to the center tap of the primary winding of transformer 226. The iirst end terminal of the secondary winding of transformer 226 is connected to the control grid of a triode 228. The second end terminal of the secondary winding of transformer 226 is connected to ground. A capacitor 229 is connected in parallel with the secondary winding of transformer 226. The cathode of triode 228 is connected to ground through a resistor 230 which is shunted by a capacitor 231. The anode of triode 228 is connected through resistors 232 and 233 to a terminal 234 which is maintained Iat a positive potential. A capacitor 235 is connected between ground and the junction between resistors 23.2 and 233. The anode of triode 228 is also connected through a capacitor 236 to the rst end terminal of a potentiometer 237. The second end terminal of potentiometer 237 is connected to ground. The contactor of potentiometer 237 is connected to the control grid of a triode 238. The cathode of triode 238 is connected to ground through a resistor 240. The anode of triode 238 is connected to terminal 234 through a resistor 241. The anode of triode 236 is also connected to ground through a capacitor 242 `and resistors 243, 244, 245, 246 and 247 which are connected in series relationship.

The circuit thus far described in Figure 6 converts a direct current input signal into an alternating signal which is amplified. The voltage dividing network formed by resistors 243, 244, 245, 246 and 247 permits output signals of different amplitudes to be yapplied to the individual servo motors. This compensates for input signals of different amplitudes. 1n one particular computer which has been constructed, the output circuit from the voltage dividing network was of the configuration lillustrated in Figure 6. The output terminals 1g, 2g 16g of the stepping switch are connected to the indicated points on the voltage dividing network.

Switch arm G is connected to the control grid of a triode 250. The cathode of triode 250 is connected to ground through a resistor 251 which is shunted by a capacitor 252. The anode of triode 250 is connected through a resistor 253 to a terminal 254 which is maintained at a positive potential. The anode of triode 250 is also connected through a capacitor 255 to the control grids of triodes 256 and 257. The cathodes of these triodes are connected to ground through a common resistor 258. The anodes of triodes 256 and 257 are connected to the respective end terminals of the secondary winding of a transformer 260. A source of alternating current 261 is directed across the primary winding of transformer 260. The center tap of the secondary winding of transformer 260 isiconnected to terminal 170. One terminal of current source 261 is connected to terminal 196, and the second terminal of current source 261 is connected through a capacitor 264 to terminal 199. Terminals 170, 196 and 199 energize servo motor 194 of Figure 5. The center tap of the secondary winding of transformer 260 is connected to a switch 265 which engages a terminal 266 when a relay 267 is energized. Terminal 199 is connected to a switch 268 which engages a terminal 269 when relay 267 is energized. Terminal 266 is connected through the rst winding 270 of two-phase induction motor 174 to ground. Terminal'269 is connccted'through the second winding 271 of motor 174 to the iirst terminal of current source 261.

The output signal of the motor drive amplifier of Figure 6 thus energizes one of the servo motors 194 of Figure 5 when a relay 192 of Figure 5 is energized. The standardization motor 174 is actuated when relay 267 is encrgized. A single servo amplifier thus energizes a plurality of motors in sequence to perform the balancing operations and standardizing function.

The stepping switch employed to establish the variables in sequence is actuated by the circuit illustrated in the lower portion of Figure 6. The cathodes of triodes 256 and 257 are connected through a resistor 280 to the coutrol grid of `a triode 281. A capacitor 282 is connected between the control grid of triode 281 and ground. The cathode of triode 281 is connected to ground through a resistor 283, and the anode of triode 281 is connected to a positive potential terminal 284 through a resistor 285. The anode of triode 281 is also connected to the first end terminal of a potentiometer 286, the second end terminal of potentiometer 286 being connected to a negative potential terminal 287.

The contacter of potentiometer 286 is connected directly to the control grid of a triode 288 and through a resistor 290 to the control grid of a triode 291. The cathodes of triodes 288 and 291 are connected to ground. The anodes of these triodes are connected to terminal 284 through a resistor 292. The anodes of triodes 288 and 291 are also connected through a resistor 293 to the control grid of la triode 294. The control grid of triode 294 is connected through a resistor 295 to ngeative potential terminal 287. The cathode of triode 294 is connected directly to ground, and the anode of triode 294 is connected through a resistor 296 to positive potential terminal 284. The anode of triode 294 is also connected through a capacitor 297 to the control grid of triode 291.

The anode of triode 294 is connected to a terminal 300 which normally is engaged by a switch 301. Switch 301 is connected through series connected resistors 302 and 303 to negative potential terminal 287. The junction between these resistors is connected to terminals 1h 211 15h. These terminals are engaged by switch arm H of the stepping switch. Switch 301 is also adapted to engage a terminal 304 which is connected to a switch 305. Switch 305 normally engages a terminal 306 which is connected through a resistor 307 to positive potential terminal 284. Switch 305 can also engage a terminal 308 which is connected to ground. Switch arm H is connected through a resistor 310 to the control grid of the triode 311. The cathode of triode 311 is connected to ground, and the anode of tiiode 311 is connected through a resistor 312 to positive potential terminal 284. The anode of triode 311 is connected through neon lamps 313, 314 and 315 and a resistor 316 to negative potential terminal 287. The junction between lamp 315 and resistor 316 is connected through a resistor 318 to the control grid of a triode 319 `and through a resistor 320 to the control grid of a triode 321. The cathodes of triodes 319 and 321 are connected to ground. The anodes of triodes 319 and 321 `are connected to the tirst terminals of a resistor 322 and solenoid 150. The second terminals of resistor 322 and solenoid are connected to the junction between a rectifier 333 `and a capacitor 334. Current source 261 is connected across the primary winding of a transformer 336. The first end terminal of the secondary winding of transformer 336 is connected through a resistor 337 to rectifier 333. The second terminal of the secondary winding of transformer 336 and the second terminal of capacitor 334 are connected to ground. A positive potential thus appears at the junction between rectiiier 333 and capacitor 334.

The anodes of triodes 319 and 321 are connected through series connected resistors 340 and 341 to the' 13 control'grids of triodes 256 and.257. A capacitor 342 is connected in parallel with resistor 341. The junction between resistors 340 and 341 is connected through a resistor 343 to negative potential terminal 287.

Terminal 16h of the stepping switch is connected 'through a resistor 345 to the grounded cathode of triode 294. Terminals 17h to 25h are connected to a tirst interrupter contact 346 of the stepping switch. The interrupter switch 347 is connected through a resistor 348 to terminals 17h to 25h. A capacitor 349 is connected in parallel with resistor 348. A resistor 350 is connected between terminals 17h to 25h and negativeA potential terminal 287.

In order to describe the switching operation, it is assumed that the input signal from one of the transducers is diiierent from the signal last applied from this particular transducer. This results in the potentiometer circuit being unbalanced so that the servo motor is energized to restore a balanced condition. At this time there is a relatively small direct current through triodes 256 and 257. The cathodes of these two triodes are thus maintained at a relatively small positive potential. This potential is inverted by triode 281 so that a potential lis applied to the control grid of triode 288 which permits this triode to conduct. Conduction by triode 288 results in the potential applied to the control grid of triode 294 being suiiiciently small to extinguish conduction by triode 294. This effectively applies a positive pulse to the control grid of triode 291 which causes it to conduct. Triodes 288 and 291 thus operate essentially in parallel. The potential at the anode of triode 294 is applied through the stepping switch to the control grid of triode 311. The decreased potential at the anode of triode 311 is in turn applied to the control grids of triodes 319 and 321 to keep these two triodes from conducting.

When the bridge circuit becomes balanced, the direct current through triodes 256 and 257 increases substantially to increase the potential applied to the control grid of triode 281. This results in the potential at the control grid of triode 288 being decreased sufficiently to extinguish conduction by this triode. However, triode 291 continues to conduct until the original charge on capacitor 297 leaks ofi. This incorporates a delay, which can be of the order of one second, for example, at the end of this period, conduction through triode 291 is extinguished so that the potential at the control grid of triode 294 is increased. The resulting conduction by triode 294 results in the potentials at the control grids of triodes 319 and 321 being increased to cause conduction through these triodes. This energizes solenoid 150 to cock the stepping switch. The resulting negative pulse at the anodes of triodes 319 and 321 is applied to the control grids of triodes 256 and 257. This negative pulse reduces the potential of the two cathodes to restore the condition initially described. This initial condition results in conduction through triodes 319 to 321 being extinguished to enable the arms of the stepping switch to move to the next contacts.

The purpose of the delay in the multivibrator formed by triodes 288 and 291 is to delay cocking of the stepping switch for a given time after the null signal level is reached at the cathodes of triodes 256 to 257. This insures that the potentiometer circuit reaches a final balanced condition before the next variable is engaged by the stepping switch. The pulse fed back to the servo amplifier from triodes 319 and 321 assures release of the stepping switch solenoid once it has been cocked. The interrupter switch 347 moves the stepping switch rapidly frorn contacts 17h to 25h and back to 1h. At position 16h, the control grid of triode 311 is connected to ground through resistors 310 and 345.

The several servo motors 194, as shown in Figure 5, are energized in sequence by the associated relay 192 being energized. These relays are actuated by triodes 360a, 360b 360h of Figure 9. The cathodes of 14 each of these triodes are connected to' ground. The anode of triode 360:1, for example, is connected toa terminal 361a which is connected to the first-terminal of relay 192 of Figure 5, the second terminal of the relay being connected to `a positive potential terminal 377. The anodes of the remaining triodes are likewise connected to a relay which energizes a respective one of the servo motors. The grids of triodes V36001,

360b 36011 are connected toV respective terminalsy 2z', 3i -15i of the stepping switch. The control grids of triodes 360o, 360b 36011 are also connected through respective resistors 362a, 362b 36211 to the junction between resistors 364 :and 365. A spare triode 360o also is provided. The second terminal of resistor 364 is connected to a negative potential 366, and a second terminal of resistor 365 is connected to ground. A capacitor 367 is connected in parallel with resistor 365.

A terminal 370 is connected to the secondary winding of transformer 336 of Figure 6. Terminal 370 is-connected through a resistor 371, a rectifier 372, and a capacitor 373 to ground. The anode of a triode 374 is connected through relay 4coil 267 to the junction ybetween rectifier 372 and capacitor 373. 'The cathode of triode 374 is connected to ground. The control grid of triode 374 is connected to terminal 1i of the stepping switch and to the control grid of a triode 375. The control grid of triode 374 is also connected to the junction between resistors 364 and 365 through a resistor -376. The anode of triode 375 is connected through relay coil 166 to the junction -between rectifier V372 and capacitor 373.v The cathode of triode 375 is connected to ground. Terminal 377 is connected between rectifier 372 and capacitor 373.

The potentiometer circuit of the computer is standardized when switch arm I engages terminal l. At this time triode 374 conducts so as to energize relay 267, see Figure 6. This connects the output signal from the amplifier of Figure 6 to standardizing motor 174. Motor 174 then adjusts resistor 180 of Figure 4 until there is a zero signal applied to the input of amplifier 168. Relay 166 is also energized at this time so that a voltage from standard Vcell 184 is Vapplied to the input of amplifier 168. This operation standardizes the potentiometer circuit of Figure 4.

Each time the arms of the stepping switch move to the next contacts, interrupter switch 347 of Figure 6 momentarily engages contact 346. This applies a positive pulse from terminal 380 of Figure 6 through a capacitor 381 to the control grid of .a triode 382 of Figure 9. The cathode of triode 382 is connected to ground. The control grid of triode 382 is connected to a negative potential terminal 390 through a resistor 383. The anode of triode 382 is connected through a resistor 384 to a positive potential terminal 385. The anode of triode 382 is also connected through a capacitor 386 to the control grid of a triode 387. The cathode of triode 387 is connected to ground. The anode and control grid of triode 387 are connected Vto terminal 385- through respective resistors 388 and 389. The anodeof triode 387 is also connected through la resistor 391 to the control grid of triode 382. The anode of triode 382 is connected through a resistor 392 to switch armI.

'I'his circuit provides a pulse which maintains the motor relay triodes 360 non-conductive for a predetermined time during and after movement of the switch arms of the stepping switch. The positive pulse from .the end of triode 382 is applied through switch arm I to cause the associated triode 360 to conduct. This delay prevents power from being applied to the servo motors 15 until switching transients in the potentiometer circuits and amplifier 168 have died out.

The computing circuit is also provided with apparatus for checking periodically the operation of the transducers and of the computer itself. With reference t Figure 4, there is shown a plurality of potentiometers 40011, 400b 4001 which are adapted to provide preset voltages. The first terminals of all these potentiometers are connected to a negative potential terminal 401. The second terminals of all these potentiometers are connected to ground. The contactors of these potentiometers are connected to the indicated k terminals of the stepping switch. Switch arm K is connected to a terminal 403. Switch 152 of Figure 4 is connected to a terminal 406 which is connected to the control grid of a triode 407 in Figure 9. Switch 159 of Figure 4 is connected to a terminal 408 which is connected to the cathode of triode 407 of Figure 9. Terminal 370 of Figure 9 is connected through a capacitor 410, an inductor 411 and a capacitor 412 to ground. The junction between capacitor 410 and inductor 411 is connected through a rectifier 413 4and a resistor 414 to terminal 408. The junction between capacitor 412 and inductor 411 is connected through a resistor 415 to terminal 406. The junction between capacitor 412 and inductor 411 is connected through a capacitor 417 to the junction between rectifier 413 and resistor 414. A potentiometer 418, having a grounded contacter, is connected between terminals 406 and 408. The anode of triode 407 is connected through a resistor 420 to terminal 385. The anode of triode 407 is also connected through resistor 421 and a neon lamp 422 to ground. The anode of triode 407 is connected through a resistor 423 to a terminal 424 which is connected to the junction between resistors 302 and 303 of Figure 6.

During one portion of the checking cycle, relay 153 is de-energized so that the signals between the a and b contacts of the stepping switch are applied between the control grid and cathode of triode 407, Figure 9. This triode normally conducts. However, if an open circuit should occur in the transducing elements, conduction by triode 407 is extinguished which increases the potential at the anode thereof. This increase in potential causes neon lamp 422 to conduct so as to provide a warning signal. The resulting positive pulse is also applied through terminal 424 to the h contacts of the stepping switch, Figure 6, to prevent the stepping switch from moving further.

The circuit which operates relays 153 and 156 of Figure 4 and relays 64 and 72 of Figure 3 is illustrated in Figure 9. Switch arm J of the stepping switch is connected to a source of positive potential 430. Terminals 1j, 2j, 3i, and 4j are connected through a resistor 431 to the control grid of a triode 432. Terminals 5j, 6j and 7]' are connected through a resistor 433 to the control grid of a triode 434. The cathodes of triodes 432 and 434 are connected to ground. The anode of triode 432 is connected by a terminal 435 through relay 72 of Figure 3 to a positive potential terminal 436. The anode of triode 434 is connected by a terminal 437 through relay 64 of Figure 3 to a positive potential terminal 438. The grids of triodes 432 and 434 are connected through respective resistors 440 and 441 to the junction between resistors 364 and 365. The control grids of triodes 432 and 434 are also connected through respective resistors 442 and 443 to the anode of a triode 445. The anode of triode 445 is connected through relay 153 of Figure 4 and a resistor 446 to a positive potential terminal 447. The anode of triode 445 is also connected through a capacitor 448 to the control grid of a triode 449. rThe cathodes of triodes 445 and 449 are connected to ground. The anode of triode 449 is connected through relay 156 and a resistor 450 to terminal 447 and to terminal 19j. Terminal 19j is also connected to a negative potential terminal 451 through resistors 452 and 453. A resistor 454 and a neon lamp'455 are connected in series relationship with one another and in parallel with resistor 450. A resistor 456 is connected between the junction between resistors 452 and 453 and the junction between resistor 450 and relay 156. The anode of triode 449 is also connected through a capacitor 458 to the control grid of triode 445.

Terminal 16]' is connected through a resistor 460 to the control grid of triode 449. Terminal 25j is connected to ground through resistors 461 and 462. A capacitor 463 is connected between the control grid of triode 449 and the junction between resistors 461 and 462. The control grid of triode 449 is also connected to a switch 464. Switch 464 is adapted to engage a terminal 465 which is connected to the junction between resistors 364 and 365 or a terminal 466 which is connected to a switch 467. Switch 467 is connected to ground when closed.

Triodes 445 and 449 form a non-stable multivibrator. Each time switch arm J engages terminal 16j current ows through resistor 460 to charge capacitor 448. Resistor 460 is extremely large so that capacitor 448 charges quite slowly. Capacitor 448 is charged to some extent each time switch arm J moves past terminal 161'. The charge on capacitor 448 thus increases stepwise. Triode 445 of the multivibrator normally conducts. This situation continues until the charge on capacitor 448 increases suliciently to cause triode 449 to conduct, which occurs after a relatively large number of cycles of the stepping switch. Conduction by triode 449 extinguishes conduc- -tion by triode 445. This energizes relay 156 and deenergizes relay 153. Under this condition, the standard voltages from the potentiometers of Figure 4 are connected in the circuit in place of the voltages from the transducers of Figure l. The output signal of the computer at this time should have a predetermined value in view of the standard input signals. Pulses generated at position 251' are coupled through capacitor 463 to the grid of triode 449 to insure that the multivibrator ilips at position 25j only and not during normal scanning of the variables (positions 2 through 15).

This overall operation of the computer is checked by means of the circuit shown in Figure 8. The second terminals of resistors 21311, 213b 213i are connected to the rst input terminal of a summing amplifier 480 which is provided with a feedback resistor 480m. The yrst output terminal of amplifier 480 is connected through a resistor 481 to the control grid of a pentode 482. The second input and output terminals of amplifier 480 are connected to ground. The control grid of pentode 482 is connected to ground through a variable resistor 483. The cathode and suppressor grid of pentode 482 are connected to ground through a resistor 484 which is shunted by a capacitor 485. The anode of pentode 482 is connected through a resistor 486 to a terminal 487 which is maintained at a positive potential. The screen grid of pentode 482 is connected to terminal 487 through a resistor 488 and to ground through a resistor 489 which is shunted by a capacitor 490.

Alternating current source 205 is connected across the primary Winding of a transformer 492. The rst end terminal of the secondary winding of transformer 492 is connected to ground through a potentiometer 493. The second end terminal of the secondary winding of transformer 492 is connected to ground. The contactor of potentiometer 493 is connected through a capacitor 494 and a resistor 495 to the control grid of pentode 482. The junction between capacitor 494 and resistor 495 is connected to ground through a resistor 496.

The anode of pentode 482 is connected through a capacitor 500 to the iirst end terminal of a potentiometer 501. The second end terminal of potentiometer 501 is connected to ground. A capacitor 502 is connected between the anode of pentode 482 and ground. The contactor of potentiometer 501 is connected to the control nected to terminal 487 through a resistor 504, and the cathode of triode 503 is connected to ground through a resistor 505 which is shunted by a capacitor506. The anode of triode S03 is connected through a capacitor 507 to the control grid of a triode 508. The control grid of triode 508 is connected to ground through a resistor 509. The cathode of triode 508 is connected to ground through a resistor 510, and the anode of triode 508 is connected to terminal 487 through a resistor 511.

The sum of the voltages from the several multiplying units of Figure 7 is thus applied to the control grid of pentode 482. A reference signal which is 180 out of phase with this summed signal is also applied to the control grid of pentode 482 from current source 205. The magnitude of the difference between the output and reference signals at junction of 481, 495 and 483 can be varied by adjustable resistor 483 to determine the magnitude of the permissible error. If the overall computer network is operating properly with the reference voltages being yapplied to the input terminals, the output signal from pentode 482 is zero. However, if an error has occurred any place in the computer network, the ltwo voltages being compared are no longer equal so that an output signal is provided by pentode 482. The amplifier circuit formed by triodes 503 and 508 is biased so that the output signal from triode 508 never exceeds a predetermined value, that is, the amplifier output is clipped.

The circuit shown in the remainder of Figure 8 forms a multivibrator which normally provides output pulses at a predetermined frequency during operation of the computer. The cathodes of triodes 513 and 514 are connected to ground. Theanode of triode 513 is connected to terminal 487 through a resistor 515, and the anode of triode 514 is connected to terminal-487 through resistors 516 and 517. The control grid of triode 513 vis connected to terminal 487 through a resistor 518. A

capacitor 519 is connected between theA anodeof triode 514 and the control grid of triode 513. A capacitor 520 is connected between the anode of triode 513 and the control grid of triode 514. Thecontrol grid of triode 514 is connected to a switch 521 which is adapted to engage terminals 522 and 523. Terminal 523 is connected to ground through a resistor 524. The checking circuit of Figure 8 is turned off when switch 521 engages iterminal 523. Terminal 522 is connected through a resistor 525 to the contactor of potentiometer 526. The rst end terrnnal of potentiometer 526 is connected through a resistor 527 to a negative potentialV terminal 528. The second end terminal of potentiometer 526 is connected through a resistor 529 to a terminal530 which is connected to the anode of triode 449 of Figure 9.

During normal operation of the computer, the bias applied to the control grid of triode 514 from potentiometers 526 is such that the multivibrator formed by triodes 513 and 514 provides an output pulse at predetermined intervals, which can be of the order of one-half second, .for example. The junction between resistors 516 and 517 is connected through a capacitor 532 to a terminal 533 which is connected to terminal 16h of Figure 6. The resulting pulses move the stepping switch past the 16th contacts. The anode of triode 508 is connected through a capacitor 535 to the positive terminal of a rectifier 536 and to the negative of ya rectier 537. The positive terminal of rectifier 537 is connected to ground. The negative terminal of rectifier 536 is connected to ground through a resistor 538 which is shunted by a capacitor 539. An outputsignal from triode 508 thus results in a negative signal appearing at the control grid of triode 514. This signal extingushes conduction through triode 514 so that the pulses applied to terminal r16h of Figure 6 are discontinued. This operates to stop further movement of the stepping switch. The flow detecting elements 61, 65 and 66 are checked when relays 64 and I72 of Figure 3 are both energized. This connects `the input of amplifier 75 to the`- contactor -of a'vpotentiometer 250". One end terminal of potentiometer 250' is connected to ground. -The second end terminal of potentiometer 250' is connected through a variable resistor 251 and a resistor 252 to the first end terminal of the secondary winding of transformer 86. A capacitor 253' is connected in parallel with resistor 252. A reference check voltage is thus applied from source 85 to the input of amplifier 75.

It should be evident from the foregoing description that many of the terminals shown areY merely for the purpose of designating connections between the severalfigures. Also, many of the switches are for the purpose of turning off portions of the apparatus or to permit manual operation for test purposes. y g

The circuit thus far described provides an automatic computation of the heat liberated by the polymerization reaction which is a direct function of the polymer production rate. The sources of heat removal fromthe reactor are indicated as signals of a rst polarity whereas the sources of heat addition are indicated as signals of av second polarity. The sum provided by the circuit of lFigure 8 thus represents the net heat of reaction. This nal signal is an alternating voltage and isapplied to a recorder-controller 215. It should be evident that in some polymerization systems, certain of the variables measured in the example normally are suficiently constant as to be omitted. The control system can thus be simplified in these applications.

In accordance with the present invention, apparatus is provided for measuring the concentration Iof polymer within reactor 30. This provides valuable information regarding the operation of the process, whichrinformation Acan vbe used to'control the catalyst flow through a valve 50 in Figure 1 and/or the ethylene ilow through a Valve S1 to maintain desired operating conditions. The

v'polymer accumulation, VdC is equal-to the input, Pd,

minus the output, CFd, where:

P'=production rate 6=time f F=product withdrawal rate :polymer concentration in reacto V=volume of reactor.

This relationship can be rewritten as follows:

This equation is solved for C by means of the analog computer of Figure 10.

Controller 215 of Figure 8 is mechanically connected to the contactor of a potentiometer 550. One end termi! nal of potentiometer 559 is lconnected to a positive potential terminal 551, and the second end terminal of potentiometer 550 is connected to ground. The potential at the contactor of potentiometer 550 is thus representative of P, the signal applied to controller 215 by the summing circuit of Figure 8. The contactor of potentiometer 550 is connected through a resistor 552 to the first input of a summing amplifier 553, the second input of -which is connected to ground. A ilowmeter 554 is associated with product conduit 40 of Figure 1 to establish a direct potential representative of the product withdrawal rate F from reactor 30. This 4direct potential is applied between a terminal 555 and ground, see Figure l0. A potentiometer 556 is connected between terminal 555 and ground. The contactor of potentiometer 5 56 is connected through unity gain sign reversal amplifier 558 and a resistorv 557 to the first input of `amplifier, 553. AThe contactor of potentiometer 556 is mechanically connected to .a recorder. 569 so as to be set by the signal applied yto recorder S60. As will become evident hereinafter, recorder 560 indicates C. The potential at the contactor of potentiometer 556 is thus representative of the product FC, whereas the potential applied therefrom to amplifier 553 is representative of FC. Amplifier 553 is provided `with a negative feedback resistor 562 of value equai to each of resistors 552 and 557 so as to `operate as a summing amplifier, the output potential being representative of P-CF.

The first output terminal of' amplifier 553 is connected to ground through a potentiometer 563. The contactor of potentiometer 563 is connected through a resistor 564 and a capacitor 565 to the first input terminal of an amplifier 566, the second input terminal of which is connected to ground. The first input terminal of amplifier 566 is connected through a resistor 567 to the contactor of a potentiometer 568. One end terminal of potentiometer 568 is connected to a negative potential terminal 569, and the second end terminal is connected to ground. Potentiometer 568 thus supplies a bias potential to the input of amplifier 566. The output potential of amplifier 553 is reduced by potentiometers 563 and 563 so that the input potential applied to amplifier 566 is representative of P--CF Amplifier 566 is provided with a feedback capacitor 572 so that the output potential of the amplifier is representative of P- CF V In one example of this computer, resistors 564 and 567 had respective values of 2,000,000 and 1,800,000 ohms, and capacitors 572 and S65 had respective values of 20 and 0.047 microfarads. The first output terminal of amplifier S66 is connected to ground through a potentiometer 573, and the second output terminal of amplifier 566 is connected directly to ground. The contactor of potentiometer 573 is connected to the first input terminal of recorder 560, the second input terminal of which is connected to ground. The potential applied to recorder 560 is thus representative of fP- CF which is C, the polymer concentration in reactor 30.

A reset circuit is provided for the purpose of calibrating the concentration computer and for observing changes in polymer concentration after a given time. A potential source 575 is applied across a potentiometer 576. The contactor and one end terminal of potentiometer 576 are connected to respective switches 577 and 578'which engage respective terminals 579 and 580 when closed. Terminals 579 and 580 are connected to the respective end terminals of capacitor 572. In normal operation, switches 577 and 578 are open. Closure of these switches results in a predetermined potential being applied across capacitor 572. This potential can then be adjusted until recorder 560 indicates a predetermined value. The subsequent change in concentration from this value can then be observed.

The apparatus of Figure thus provides valuable information regarding the concentration of polymer in the reactor at any given time. tion, suitable adjustments can be made to retain polymer production at a given level. Amplifiers 553 and 566 can be conventional high gain D C. amplifiers.

While the invention has been described in conjunction with a present preferred embodiment, it obviously is not limited thereto.

What is claimed is:

1. A computer for use in measuring the concentration of polymer within a reactor in a continuous polymerization reaction wherein material to be polymerized is ln response to this informaintroduced into a reactor and polymer is withdrawn from the reactor comprising means to establish a first signal representative of the rate of polymer production within the reactor, means to establish a second signal representative of the rate of withdrawal of polymer from thc reactor, means to integrate to establish a third signal, means to multiply said second signal by said third signal to establish a fourth signal, means to subtract said fourth signal from said first signal to establish a fifth signal, means to divide said fifth signal by a constant representative of the volume of the reactor to establish a sixth signal, and means to apply said sixth signal to the input of said means to integrate, said third signal being representative of the concentration of polymer in the reactor.

2. A computer for use in measuring the concentration of polymer within a reactor in a continuous polymerization reaction wherein material to be polymcrized is introduced into a reactor and polymer is withdrawn from the reactor comprising means to establish a first potential representative of the rate of polymer production within the reactor, means to establish a second potential representative of the rate of withdrawal of polymer from the reactor, means to integrate, means responsive to the output of said means to integrate to attenuate said second potential, thereby to establish a third potential representative to the product of said second potential and the output signal of said means to integrate` potential subtracting means, means to apply said first and third potentials to said subtracting means so as to establish an output fourth potential representative of the difference between said first and third potentials, means to attenuate said fourth potential by a factor representative of the volume of the reactor so as to establish a fifth potential, means to apply said fifth potential to the input of said means to integrate, and means to indicate the output of said means to integrate, said output being representative of the concentration of polymer within the reactor.

3. The computer of claim 2 wherein said means to integrate comprises a recorder; and said means to attenuate said second potential comprises a potentiometer having said second potential applied across the end terminals thereof, and means responsive to the position of said recorder to adjust the contactor of said potentiometer. the potential between the contactor and one end terminal of said potentiometer being said third potential.

4. The computer ofclaim 2 wherein said means to integrate comprises a high gain D.C. amplifier, a resistor connected in the input circuit of said amplifier, and a capacitor connected between the output and input of said amplifier to form a feedback path, said resistor and capacitor establishing the time constant of said means to integrate.

5. The computer of claim 4 further comprising a variable source of direct potential, and switching means to apply said source of direct potential selectiveiy across said capacitor so that the positive terminal of said source is connected to the output of said amplifier.

6. A polymerization system comprising a reactor; first conduit means communicating with said reactor to introduce material to be polymerized; second conduit means communicating with said reactor to introduce a catalyst; third conduit means communicating with said reactor to introduce a diluent; means to agitate the material within said reactor; fourth conduit means in theiinal contact with said reactor to circulate a coolant in heat exchange relationship with said material; fifth conduit means communicating with said reactor to remove polymer from vsaid reactor; means to establish a first signal representameans, means to measure the temperature and flow rate of the diluent passed through said third conduit means, means to measure lthe temperature of said reactor, means to measure the heat `added to said reactor by said means to agitate the material therein, means to measure the heat lost from said reactor to the surrounding atmosphere, means to measure the ilow of coolant through said fourth conduit means and the temperatures of the coolant supplied to and removed from said reactor, and means responsive to said means to measure to compute the diierence between heat removed from said reactor and the heat supplied to said reactor, thereby to establish said first signal; means to establish a second signal representative of the rate of withdrawal of polymer from said zone through said fth conduit means; means to integrate to establish a third signal; means to multiply said second signal by said third signal to establish a fourth signal; means to subtract said fourth signal from said first signal to establish a fth signal; means to divide said fth signal by a constant representative of the volume of said reactor to establish a sixth signal; and means to apply said sixth signal to the input of said means to integrate, said third signal being representative of the concentration of polymer in said reactor.

7. A polymerization system comprising a reactor; means to introduce material to be polymerized and catalyst to said reactor; means to remove the resulting products from said reactor; means to establish a second signal representative of the rate of polymer production within said reactor which comprises means to measure the heat supplied to said reactor, means to measure the 22 heat removed from said reactor, means to measure the diierence between the heat supplied and the heat rcmoved, thereby to establish said rst signal; means to establish a second signal representative of the rate of withdrawal of polymer from said reactor; means to inte-V grate lto establish a third signal; means tomultiply said second signal by said third signal to establish a fourth signal; means to subtract said fourth signal from said iirst signal to establish a fifth signal; means to divide said fth signal by a constant representative of the volume of said reactor to establish a sixth signal; and means to apply said sixth signal to the input of said means to integrate, said third signal being representative of the concentration of polymer in said reactor.

Electronic Analog Computers (Korn and Korn), 1952, pp. 15, 3l and 288-292. 

1. A COMPUTER FOR USE IN MEASURING THE CONCENTRATION OF POLYMER WITHIN A REACTOR IN A CONTINUOUS POLYMERIZATION REACTION WHEREIN MATERIAL TO BE POLYMERIZED IS INTRODUCED INTO A REACTOR AND POLYMER IS WITHDRAWN FROM THE REACTOR COMPRISING MEANS TO ESTABLISH A FIRST SIGNAL REPRESENTATIVE OF THE RATE OF POLYMER PRODUCTION WITHIN THE REACTOR, MEANS TO ESTABLISH A SECOND SIGNAL REPRESENTATIVE OF THE RATE OF WITHDRAWAL OF POLYMER FROM THE REACTOR, MEANS TO INTEGRATE TO ESTABLISH A THIRD SIGNAL, MEANS 